Stretch-activated channels in single early distal tubule cells of the frog.

1. Single stretch-activated channels have been studied in cell-attached and excised patches from single early distal tubule (diluting segment) cells of Rana temporaria. 2. The channels can be reversibly activated, in both cell-attached and excised patches, by the application of negative pressure to the pipette causing mechanical stretching of the cell membrane. In cell-attached patches, application of 14.8 cmH2O negative pressure to the patch pipette increased reversibly the open probably from 0.11 to 0.87. 3. The channel conductance in the cell-attached configuration with standard Ringer solution in the pipette is 21.3 pS. 4. The channel is non-specific. In excised inside-out patches ion substitution experiments show that the channel does not discriminate between sodium and potassium ions, nor does it appear to select for cations over anions. 5. The channel is voltage sensitive such that depolarizing the cell opens the channel. The open probability at the resting membrane potential, 0.89, was reduced to 0.26 at a hyperpolarizing potential of 100 mV (holding pressure of -20.1 cmH2O or -206 Pa). 6. The sensitivity of the channel to mechanical stretching suggests that the channel may be involved in cell volume regulation.